The mechanism of action of animal collagenolytic enzymes, their site of formation, and their physiologic regulation, using as a model system the collagenase involved in tissue resorption in amphibian metamorphosis will be studied. The knowledge acquired in this investigation will then be utilized for the study of mammalian collagenases also isolated and partially characterized in this and other laboratories. I plan to: a) Identify the cell of origin, intracellular sites of synthesis and specific sites of extracellular action of the enzyme in animals undergoing thyroxine stimulated metamorphosis. b) Examine the amino acid sequence around the specific site of enzymatic cleavage of the collagen molecule to obtain information as to the substrate structural requirements. c) Investigate the specificity of attack on native collagen and its separated alpha chains cyanogen bromide peptide fragments of the alpha chain and renatured segments of the polypeptide. d) Study possible interrelationship of subunits of the enzyme and the role of metals in the activity of the enzyme. e) Extend, in the future, the knowledge acquired here to enzymes which degrade other structure proteins, such as elastin and myosin. f) Gain some understanding of the regulatoy mechanism for the metabolic control of collagen degradation.